Taxes (Details 2) - Deferred Taxes (USD $)	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Share-based compensation	$ 23,487,000	$ 17,703,000
Accounts receivable	1,275,000	1,232,000
State income taxes	2,293,000	590,000
Vacation accruals	5,235,000	4,033,000
Deferred revenue	3,793,000	3,815,000
Deferred rent	13,736,000	10,477,000
Accruals not currently deductible	7,850,000	7,212,000
Net operating loss carryforwards	3,534,000	5,697,000
Charitable contribution carryforward	754,000	782,000
Foreign tax credit	1,723,000	1,583,000
Research and development credits	13,871,000	3,401,000
Other	1,674,000	(348,000)
Total gross deferred tax assets	79,225,000	56,177,000
Deferred tax liabilities:
Depreciation	125,209,000	108,208,000
Share-based compensation	107,000	821,000
Prepaids	2,981,000	2,593,000
Total gross deferred tax liabilities	128,297,000	111,622,000
Net deferred tax assets (liabilities)	(49,072,000)	(55,445,000)
Valuation allowance
Valuation allowance on deferred tax asset	0
Deferred Tax Liability Not Recognized, Undistributed Earnings of Foreign Subsidiaries
Deferred tax liability recognized for undistributed earnings of foreign subsidiaries	0
Undistributed earnings of the company's foreign subsidiaries considered indefinitely invested	175,500,000
Federal
Operating Loss and Tax Credit Carryforwards
Net operating loss carryforwards	250,800,000
Tax credit carryforwards	15,600,000
Foreign
Operating Loss and Tax Credit Carryforwards
Net operating loss carryforwards	$ 21,400,000